The United Nations Security Council has approved a resolution calling for a 30-day cease-fire in Syria, following one of the bloodiest weeks of aerial bombardment in the war that has devastated the country.

In the eastern suburbs of Damascus, a region called Eastern Ghouta, nearly 500 people have been killed in a deadly escalation by the Syrian government that began Sunday, the Syrian Observatory for Human Rights told The Associated Press. More than 120 of the dead are children, the group says.

The Security Council resolution aims to get humanitarian aid to Eastern Ghouta and other areas under siege. The resolution was delayed several times in an effort to get Russia's approval.

"Airstrikes, artillery shells and barrels filled with TNT are being dropped on neighborhoods that are heavily populated by civilians who have no way to escape," NPR's Lama Al-Arian reports. "They're being forced into bunkers, and many of them can't even find the time to bury their dead."

Syria's Civil Defense, a volunteer rescue group known as the White Helmets, told Reuters that it counted at least 350 deaths in a four-day span earlier in the week.

"Maybe there are many more," Siraj Mahmoud, a civil defense spokesman, told the news service. "We weren't able to count the martyrs yesterday or the day before because the warplanes are touring the skies."

Rescuers hurry to pull people from rubble, a difficult task amid the unrelenting barrage.

"But if we have to go out running on our legs and dig with our hands to rescue the people, we will still be here," Mahmoud told Reuters.

United Nations Secretary-General António Guterres called for an immediate end to hostilities in the region so the sick and wounded can be evacuated.

"I am deeply saddened by the terrible suffering of the civilian population in Eastern Ghouta — 400,000 people that live in hell on earth," he said to the U.N. Security Council on Wednesday. "I don't think we can let things go on happening in this horrendous way. "

Syrian state media said rebel factions had fired shells at the Old City of Damascus on Saturday, Reuters reported.

The Security Council's resolution, which passed 15-0, demands "all parties cease hostilities" for at least 30 days throughout Syria to allow the safe delivery of humanitarian aid and evacuations of the critically sick and wounded.

The resolution, sponsored by Kuwait and Sweden, calls for all parties to immediately lift sieges of populated areas, including Eastern Ghouta. The cease-fire does not apply to military operations against ISIS, al-Qaida and other terrorist groups.

A vote on the resolution was delayed Friday as its sponsors worked to get a version Russia would approve. As NPR previously reported, most members of the Security Council had wanted to require the cease-fire to go into effect within 72 hours, but Russia had pushed for a looser timeline.

U.S. Ambassador to the U.N. Nikki Haley criticized Russia for the wait, saying it had cost lives, The Associated Press reports.

The break in fighting will come at a crucial time for Ghouta's civilians.

"There is no electricity, no water, no flour, no bread and no baby formula," paramedic Siraj Mahmoud told the AP. "There is nothing inside Ghouta."

A group of doctors and medical activists, from institutions including Harvard and Johns Hopkins, published an appeal on Friday to end the suffering in Ghouta. They urged citizens and health professionals to pressure government officials to act and for the U.N. Secretariat to use more effective tactics.

"Inaction in the face of unrelenting attacks on civilians represents an epic failure of world leaders," they write in The Lancet. "The UN Security Council has utterly failed the people of Syria. The UN Secretariat seems to operate without an effective strategy for political negotiations or aid delivery. These compounded failures are increasing frustrations with the UN as a legitimate interlocutor on human rights violations everywhere, and translate into deaths and suffering. We cannot allow this situation to continue."